This application relates to the field of delivering self-expanding stents into a body lumen of a patient. More specifically, the invention relates to providing a system for continuous stent advancement during delivery, and also for retraction of a sheath that confines the stent.
The broad concept of delivering a self-expanding stent into a body lumen of a patient is known in the art. Typically, self-expanding stent delivery involves pushing a stent so that the stent moves distally out of a confined condition within a sheath of a delivery catheter, into an expanded condition in the patient's body lumen. Typically, a delivery device is configured to push the stent distally.
However, various problems arise when this action is carried out by a delivery device that hooks (via a stent-engagement member) into the mesh of a stent before a distal force is applied to the stent-engagement member and hence to the stent.
First, a stent-engagement member that is positioned towards the rear (proximal) end of the stent may have the effect, when it is moved distally, of compressing the proximal end of the stent rather than moving the entire stent distally. This may be caused by the fact that friction against the sheath holds the distal end of the stent stationary in relation to the delivery catheter.
Second, if a stent-engagement member is positioned to engage the stent towards the front end of the stent in order to avoid the problem of compression identified above, then the stent engagement member must be made to oscillate backwards and forwards in short strokes in order to keep the stent-engagement member in contact with the mesh of the stent. (It will be appreciated that that the expansion of the stent will cause the stent-engagement member to disengage from the stent.) This oscillation requirement introduces further complexity in that the user physician must keep track of how many times he has moved the stent, and the distance of each oscillation.
Thus both methods of forcing a stent distally out of a confining sheath during deployment of a self expanding stent from a catheter are beset by problems. There is accordingly a need for a self expanding stent delivery system that address the problems in the art. The present invention addresses these and other needs.